As a pump for sucking in and discharging fluid, there is known a vane pump which includes a housing having a suction port and a discharge port, a cam ring arranged in the housing and having a cam face at an inner circumferential face, a rotor arranged in the cam ring and driven rotationally, a shaft (a rotary shaft) rotatably supported on the housing so as to rotate the rotor, and a plurality of vanes arranged movably advance or retreat from an outer circumferential face of the rotor in a radial direction and coming into slide contact with the inner circumferential face (i.e. the cam face) of the cam ring, the housing being provided with a return channel (return passage) which returns a portion (divided flow) of working fluid discharged from the discharge port so as to flow together with sucked fluid sucked in from the suction port in a direction perpendicular to a flow direction of the sucked fluid (for example, see Patent Document 1).
In this vane pump, it is adopted that a piping system in which a flow control valve is arranged between a discharge side piping connected to the discharge port of the housing and a return piping connected to the return channel of the housing. When the rotor is rotated at high speed and the discharge flow rate becomes more than a predetermined rate, the flow control valve is opened and a portion of the working fluid flowing through the discharge side piping is divided to flow into the return piping side, and the working fluid divided into the return piping is flowed together with sucked fluid flowing in from the suction port, and then the fluid flowed together is led to a pump chamber through a suction channel.
However, in the vane pump and the piping system, because the sucked fluid flowing in from the suction port and the returned fluid flowing in from the return channel merge at right angles to each other, the flow of the sucked fluid flowing in from the suction port is obstructed, and there are risks causing a disorder of the flow (turbulence) and an increase of flow loss or the like and therefore lowering of the pump efficiency.